1. Field of the Invention
This invention relates to polishing pads and, more particularly, to polishing pads made from resin impregnated nonwoven material.
2. Description of the Prior Art
Integrated circuits are prepared primarily from pure silicon or germanium which is crystalline in form. Typically, the base for such integrated circuits is a slice or wafer of single crystalline silicon or germanium. A typical method of manufacturing the base is by starting with a single crystalline seed to produce a single crystal ingot. Typically, the single seed is placed in a silicon or germanium melt while appropriately orienting the crystal and maintaining the particular temperature in order to grow the crystal. In this manner, a single crystal ingot of 1 or 2 inches in diameter and several inches in length is produced. The cut wafers are about 10 mils thick or less. After slicing, the wafers are polished.
In polishing the wafers, the wafers are mounted on a flat surface such as a table or the like which has been moistened with water. The capillary action of the water adheres the individual wafers to the table. A polishing pad is placed in circular motion and contacts the wafers while an abrasive dispersion or slurry is injected so that the abrasive is interposed between the pad and the wafer. The polishing surface of the pad must be porous so that it can absorb the dispersion or slurry and act as a reservoir for supplying the dispersion or slurry at the interface between the pad and the wafer. The characteristics of the polishing pad are critical in that they must have an extremely smooth polishing surface. Further, the frictional and porosity characteristics of the pad are important because if the pad grips the wafers, the capillary force may be overcome and the wafers thrown from the table. PG,3
In accordance with the present invention, a polishing pad is provided which has a very smooth yet porous surface and the appropriate frictional characteristics required for the polishing of silicon or germanium wafers used as semi-conductors in integrated circuits.